<h2>购物车添加</h2>
<form action="/cart/add" method="get">
  user_id<input type="text" name="user_id"><br>
  product_id<input type="text" name="product_id"><br>
  count<input type="text" name="count"><br>
  is_checked<input type="text" name="is_checked"><br>
  <input type="submit">
</form>